Rotary piston engine



April 3, 1934. H. WALTER ROTARY PISTON ENGINE Filed April 20, 1932 2 Sheets-Sheet l April 3, 1934. H. WALTER ROTARY PISTON ENGINE Filed April 20, 1932 2 Sheets-Sheet 2 Patented Apr. 3, 1934 UNITED STATES PATENT OFFICE ROTARY PISTON ENGINE Application April 20, 1932, Serial No. 606,495 In Germany April 24, 1931 8 Claims. (Cl. 230-150) The invention relates to rotary piston engines, for instance compressors, of the type in which a working piston and a controlling piston operate in a common casing consisting of two cylindrical 8 portions. These two pistons revolve in the same direction and at the same angular velocity. 'The working piston has a drop-shaped cross section and the controlling piston is bounded by two cylindrical surfaces, a tightening edge or a narrow l tightening surface being provided on the working piston, while the controlling piston is formed with two tightening edges.

According to the invention, a rotary piston engine of the type outlined, for instance a compressor, is constructed in such a manner, that the Working piston, during the period of time beginning with the termination of the delivery of the fluid into the pressure conduit and ending with the commencement of the new compression stroke, executes an idle motion in the suction space. During this period all spaces situated between the two pistons and the casing Wall are in communication with the suction space, so that compression cannot occur in any of these spaces, until that space has been shut off by the controlling piston, the working piston and the easing, the content of which can be forced out nearly completely by the working piston.

In order that the invention may be clearly understood and readily carried into effect, two embodiments of the same are illustrated schematically in the accompanying drawings by way of example. In these drawings Figures 1 to 4 are sections of the new rotary piston engine forming the first embodiment, with the cooperable pistons in difierentpositions,

Fig. 5 shows another embodiment in a similar section, while 1 Figures 6 and 7 are sections of two different multi-piston engines designed according to the invention.

Referring first to Figures 1 to 4, the casing of the rotary engine comprises two hollow cylindrical portions 1 and 2 which merge into eachother and are formed with a large suction opening 6 and a small delivery opening socket 7. A working piston 3, fixed on a shaft 14, is mounted for rotation in the portion 1 of the casing and concentric thereto. The pear-shaped cross section of piston 3 is bounded by three arcs 8, 9 and 10 of corre sponding circles having radii d, b, and a, as may be seen in Figure 1. The edge 4 of piston 3 extends with a suitably. slight clearance up to the wall of the part 1 of the casing. A controlling piston 5, fixed on shaft 13, is revolubly mounted in the part 2 of the casing, with the shaft 13 in the center of that part of the casing. The outer surface of piston 5 is bounded by two arcs 11, 12 of corresponding circles having radii e, c. The radii of curvature a, b, c of the cylindrical surfaces 9, 10 and 12 60 are of equal length and have the points z, y and w for their respective centers. Also the sum of the radii of curvature d and e of the cylindrical surfaces 8 and 11 is equal to the distance v--:c existing between the centers of the shafts 13 and 14. 5 The two pistons 3 and 5 are fixed to their shafts in such a manner, that the plane of symmetry of the working piston in all mutual positions which the pistons 3 and 5 assume during operation,is normal to the plane passing through the edges 19and 25 of the controlling piston 5, as marked by chaindotted lines in Figure 2. The passage area of the socket 7 is subdivided by a partition 16 so that a large and a small outlet area are formed which areas are positively controlled by flaps or valves 17 and 18, the controlling motion being derived for instance from the shaft l i of the working piston by suitable means. This means may be in the form of cam disks 2'? and 28 with which cooperate rectilinearly-guided and spring-operated 8i) rods 37 and 38, which are jointed to levers 47 and 48, respectively, which are in turn mounted on the pivots of the flap valves 17 and 18. A gear transmission for the control of these valves as is well known in the prior art may also be availed of The mode of operation of the rotary piston engine hereinbefore described will be seen from Figures 1 to 4, the engine acting as compressor if the pistons 3, 5 revolve in the direction indicated by the arrows. The fluid to be compressed enters the casing through the inlet socket 6. From the instant the edge 4 of working piston 3 passes past edge 15 of the casing, Figure l, and the edge 19 of the controlling piston 5 arrives at the merging edge 20 of the two casing parts, the compression chamber 21 is shut off and compression occurs and lasts until the pistons 3. 5 have reached the position illustrated in Figure 2. At that instant the pressure of the compressed fluid has reached the desired maximum amount, whereupon the flaps 17 and 18 are opened and delivery begins. After the pistons 3, 5 then have reached the position shown in Figure 3, flap 17 closes the large passage of socket 7 so that the fluid under pressure existing in space 21 is forced out through the passage controlled by flap 18, except the small remainder shown in Figure 4. In the further course of the pistons beyond the position of Figure 4, also flap 18 is closed and this small remainder of fluid still present in the small triangu- 11G lar space 21 escapes through the gaps existing between the pistons and the casing and expands. Now, in the subsequent idle run of the pistons 3 and 5 there are no closed spaces between the pistons and the casing. On the contrary, all spaces are in communication with the suction socket, so that no work is done by the engine until the edge 4 of the working piston has again reached the wall edge 15 and the edge 19 of piston 5 the wall edge 20. The pistons then assume again the position illustrated in Figure 1, whereupon the described cycle recommences.

In order to obtain a larger tightening surface of the working piston 3 on the casing, a narrow cylindrical surface 22 may be provided on the piston 3 instead of the edge 4, as represented in Figure 5. Consequently, in this modification the two flanks 9a and 10a of piston 3 do not intersect at the edge of the casing wall, but only outside the casing. The centers of curvature y and 2 of the former flanks 9 and 10, Figure 1, therefore are displaced on a circle drawn about the center :0 of piston 3 to the position marked by y and 2 The radii a and a of the cylindrical flanks 9a and 10a, however, remain equal to the distance 12-3: of the shafts l3 and 14 of the two pistons. Owing to the modified shape of the working piston 3 the controlling piston, in lieu of the cylindrical flank 12 of the first embodiment is formed with a flank composed of two cylindrical sections 23 and 24 concentric to the respective centers to and w", with the radii c, c, and crossing the flank 11 in the controlling edges 19 and 25'.

Since the flank 12 of the controlling piston of the first embodiment and the flanks 23, 24 of the modification need not effect a tight closing in contrast to the flanks 9, 10 or 9a and lOa'of the working piston 3, they may have another suitable cross-sectional configuration, if required for any special reason, as for instance reduction of the weight of the controlling piston. However their contours may not extend beyond the cylindrical surfaces 12 or 23, 24 since otherwise the pistons 3 and 5 would not co-operate. The shape of the edges 19 and 25 and, respectively, 19' and 25' of the modification, however, must not be altered, since these edges are tightening edges.

The described rotary piston engine is remarkable for the very simple shape of the co-operating parts, that is of the pistons 3 and 5 and casing 1, 2, all boundary surfaces of which are simple cylindrical surfaces and therefore easy and economical to manufacture. A further advantage resides in the fact that in consequence of the peculiar co-operation of the two pistons 3 and 5, of the subdivision of the outlet passage '7 in connection with the control of the flaps 17 and 18 only an extremely small clearance exists in the engine in contrast to known engines of the same type, and that in every compression stroke the compressed fluid is forced out of the compression chamber approximately without any remainder. Finally, when compared with known engines of this type, particularly blowers, in which co-operate a very big working piston of a similar shape and a very small controlling piston likewise of similar shape, the present engine affords the advantage that during the idle run of the pistons no closed chamber is formed in which as in the known engines part of the fluid is first compressed and then expands again within the engine.

Instead of the flaps 1'7, 18 other suitable controlling members may be provided in the outlet opening, such as rotary slides or the like, provided they are actuated in a manner corresponding to the actuation of the flaps 1'7 and 18. Needless to say that the described rotary engine is adapted to work also as a prime mover for which purpose the direction of rotation of the pistons has to be reversed.

Figures 6 and 7 show examples of multi-piston engines designed according to the invention. In these engines two or more working piston 3 cooperate with a common controlling piston 5. Arrangements of this kind are remarkable for a very good utilization of space and reduction of weight and manufacturing costs.

What I claim as my invention is:-

1. A rotary piston engine comprising a casing composed of two cylindrical portions of substantially the same order of magnitude, a rotating shaft concentrically mounted in each of said cylindrical portions adapted to rotate in the same direction and at the same angular velocity, a pear-shaped Working piston having at least a tightening edge mounted on one of said shafts in one cylindrical portion, said working piston having for the radius of curvature of the cylindrical portion closest said one shaft a fraction in the vicinity of one-half of the radius of curvature of the cylindrical portion containing said piston, a controlling piston bounded by cylindrical surfaces and having two tightening edges, mounted on the other of said shafts in the second cylindrical portion, one of said cylindrical surfaces being congruous with said second cylindrical portion of said casing and approximately subtended by the diameter of said cylindrical portion, an edge in said casing at the junction of said cylindrical portions, said last-mentioned one of said cylindrical surfaces furthermore having a radius of curvature which is equivalent to the difference of the distance between said rotating shafts and the first-mentioned radius of curvature of said working piston, inlet and outlet fluid openings in said cylindrical portion containing said working piston, said working and controlling pistons being so mounted upon the rotating shafts that the tightening edge upon the working piston cooperates with one of said fluid passages simultane ously With the coincidence of one of said tightening edges upon said controlling piston with said casing edge.

2. A rotary piston engine comprising a casing composed of two cylindrical portions of substantially the same order of magnitude, a rotating shaft concentrically mounted in each of said cylindrical portions adapted to rotate in the same direction and at the same angular velocity, a pear-shaped working piston having at least a tightening edge mounted onone of said shafts in one cylindrical portion, a controlling piston, bounded by cylindrical surfaces and having two tightening edges, mounted on the other of said shafts in the second cylindrical portion, one of said cylindrical surfaces being congruous with said second cylindrical portion of said casing and approximately subtended by the diameter of said portion, an edge in said casing at the junction of said cylindrical portions, two serially arranged passages near said edge in said first-mentioned cylindrical portion, valves for controlling said passages, means for controlling said valves to open the passage adjacent the edge at least at all times that the passage remote from the edge is open, to close the second passage at least at all times that the first passage is closed, and to close the second passage during the travel of the tightening edge of the working piston adjacent thereice Mill

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to, said working and controlling pistons being so mounted upon their respective shafts that the tightening edges thereof control the closing of a chamber defined by said two pistons and casing wall, and an opening of large angular extent in said casing wall at the side thereof opposite said edge.

3. A rotary piston engine comprising a casing composed of two cylindrical portions of substantially the same order of magnitude, a rotating shaft concentrically mounted in each of said cylindrical portions adapted to rotate in the same direction and at the same angular velocity, a pear-shaped working piston having at least a tightening edge mounted on one of said shafts in one cylindrical portion, a controlling piston, bounded by cylindrical surfaces and having two tightening edges, mounted on the other of said shafts in the second cylindrical portion, one of said cylindrical surfaces being congruous with said second cylindrical portion of said casing and approximately subtended by the diameter of said portion, an edge in said casing at the junction of said cylindrical portions, two serially arranged passages near said edge in said first-mentioned cylindrical portion, said passages being of different size with the smaller one adjacent said edge, valves for controlling said passages, means for controlling said valves to open the passage adjacent the edge at least at all times that the passage remote from the edge is open, to close the second passage at least at all times that the first passage is closed, and to close the second passage during the travel of the tightening edge of the working piston adjacent thereto, said working and controlling pistons being so mounted upon their respective shafts that the tightening edges thereof control the closing of a chamber defined by said two pistons and casing wall, and an opening of large angular extent in said casing wall at the side thereof opposite said edge.

4. A rotary piston engine comprising a casing composed of two cylindrical portions of substantially the same orderof magnitude,a rotating shaft concentrically mounted in each of said cylindrical portions adapted to rotate in the same direction and at the same angular velocity, a pear-shaped working piston having at least a tightening edge mounted on one of said shafts in one cylindrical portion, a controlling piston, bounded by cylindrical surfaces and having two tightening edges, mounted on the other of said shafts in the second cylindrical portion, one of said cylindrical surfaces being congruous with said second cylindrical portion of said casing and approximately subtended by the diameter of said portion, a fluid inlet of large angular extent intercepting said cylindrical portions of said casing at one side thereof, a fluid outlet in said first-mentioned cylindrical portion at the other side of the casing, said working and controlling pistons being so mounted upon their respective shafts that the tightening edges thereof control the closing of a chamber defined by said two pistons and the casing wall from the start of the compression stroke to the conclusion of the expulsion of the fiuid by the working piston. and that for the remainder of the cycle all space in the casing not occupied by the pistons is in communication with the fluid inlet.

5. The combination claimed in claim 4 wherein said fluid outlet comprises a plurality of serialpiston.

6. The combination claimed in claim 4 wherein said outlet comprises a plurality of serially arranged outlet passages of different extent, said passages successively decreasing in extent in the direction of angular movement of the working piston, valves for controlling said outlet passages,-

and means for controlling said valves to maintain said passages closed during the compression stroke of the working piston, to simultaneously open said passages upon completion of said compression stroke, and to successively close said passages in the order of their decreasing dimensions as the tightening edge of the working pistons arrives thereat.

'7. The combination claimed in claim 4 wherein said fluid outlet comprises two serially arranged outlet passages of different extent, the smaller passage being ahead of the larger in the direction of angular movement of the working piston, and

means for controlling said valves to maintain said passages closed during the compression stroke of the working piston, to simultaneously open said passages upon completion of the compression stroke, and to successively close said larger and smaller passages, respectively, as the tightening edge of the working piston arrives thereat.

8. A rotary piston engine comprising a casing composed of a plurality of exterior cylindrical portions and a centrally disposed cylindrical portion common thereto, a rotating shaft concentrically mounted in each of said cylindrical portions adapted to rotate in the same direction and at the same angular velocity, a pear-shaped working piston having at least a tightening edge mounted upon each of said shafts in said exterior cylindrical portions, a controlling piston, bounded by cylindrical surfaces and having two tightening edges, mounted upon said shaft in said centrally disposed cylindrical portion, one of said cylindrical surfaces being congruous with said last-mentioned cylindrical portion of said casing and approximately subtended by the diameter of said portion, a fluid inlet of large angular extent in each of said exterior cylindrical portions evenly distributed about said centrally disposed portion, a fluid outlet in each of said exterior cylindrical portions in the sides opposite said fluid inlets, said working and controlling pistons being so mounted upon their respective shafts that the tightening edges of said plurality of working pistons in conjunction with the tightening edges of said controlling piston successively control the closing of a pluraity of chambers defined by said pistons and casing wall from the start of the compression stroke in each exterior cylindrical portion to the conclusion of the expulsion of the fluid by the respective working piston, and that for the remainder of the cycle all space in the respective exterior cylindrical portions and central portion not occupied by the pistons is in communication with the fluid inlets.

HELLMUTH WALTER. 

